water supply to griet

8/13/2019 Water Supply to GRIET

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DESIGN OF WATER SUPPLY AND SANITATION SYSTEM TO

THE BLOCK IV OF GRIET CAMPUS

Aishwarya Manasa Preethi Spandana Mrudula honey

ABSTRACT

The basic aim of the project is to provide drinking water supply and sanitation system by

estimating the daily water requirement for the building. The study area considered is block IV of

GRIET.

For an effective water supply network, pipe network analysis is done. Pipe network

analysis is the fluid flow through a hydraulics network containing several or many

interconnected branches whose aim is to determine the flow rates and pressure drops in the

individual sections of the network. Hardy cross method is the classical approach for solving the

networks. However the problem can be addressed by using specialized software such as

EPANET and LMNO in order to automatically solve the problems.

Sanitation system is equally important to water supply system. Well planned sanitation

system ensures good health of the people, i.e by putting all the health hazards at bay. Also

improves the architectural beauty by not causing any inconvenience.


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LIST OF FIGURES

Name of the figure

2.3.1 Dead end system

2.3.2 Grid iron system

2.3.3 Circular system

2.3.4 Radial system

2.4.1 Gravity system

2.4.2 Pumping system

2.4.3 Dual system of distribution

2.10.1.1 Sluice valve

2.10.1.2 Check valve

2.10.1.3 Air valve

2.11 Post hydrant

2.11.1 House water connection

2.11.2 Stop cock

2.11.3 Bib cock

2.11.4 Pipe fittings

2.11.5 Piping system using overhead tank

2.12.2 Loss of head due to sudden enlargement

2.12.3 Loss of head due to sudden contraction

3.1 A view of block IV

3.2 Plan of block IV

3.3 Elevation of block IV

3.4 Plan of terrace

3.5 Plan of washroom in ground floor


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3.6 Plan of washroom in first floor

3.7 Plan of washroom in second floor

3.8 Plan of washroom in third floor

3.9 Plan of washroom in fourth floor

5.1.1 Pipe network

5.1.2 Pipe network

5.1.3 Pipe network

5.3.1 Septic tank

5.3.2 Pipe line layout


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Acknowledgement

It gives us immense pleasure to express our gratitude to professor Dr. G. Venkata Ramana,

Head of the department of Civil Engineering for his esteemed guidance and able supervision

during the course of the project. We would like to express our sincere thanks for providing us an

opportunity to complete our industrial oriented main project successfully, which is a part ofcourse curriculum.

We are especially thankful to our principal Dr.J.N.Murthyfor providing the necessary facilities

to carry out the work successfully.

This training would not have been successfully completed without the guidance and support of

Mr.Nookaraju Professor of Mechanical engineering department.

Mr.Venkat raju Incharge of Strength of materials laboratory.

Mr. Prasad Sr. Plumber.

We are deeply indebted to our project team members who were always ready to help us during

project time.


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INTRODUCTION


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Chapter 1

Introduction

1.1 General

Need for protected water supply

Protected water supply means the supply of water that is treated to remove the

impurities and made safe to public health.

Pure and whole some water is to be supplied to the community alone can bring down the

morbidity rates

1.2 Objectives of the community water supply system

1. To provide whole some water to the consumers for drinking purpose.

2. To supply adequate quantity to meet at least the minimum needs of the

individuals

3. To make adequate provisions for emergencies like fire fighting, festivals,

meeting etc.

4. To make provision for future demands due to increase in population, increase in

standard of living, storage and conveyance

5. To prevent pollution of water at source, storage and conveyance

6. To maintain the treatment units and distribution system in good condition with

adequate staff and materials

7. To design and maintain the system that is economical and reliable water


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1.3 Wholesome water

wholesome water is defined as the water which contains the minerals in small quantities at

requisite levels and free from harmful impurities Chemically pure water is also corrosive but not

whole some water. The water that is fit for drinking safe and agreeable is called potable water.

1.3.1 The following are the requirements of wholesome water

1. It should be free from bacteria

2. It should be colourless and sparkling

3. It should be tasty, odour free and cool

4. It should be free from objectionable matter

5. It should not corrode pipes

6. It should have dissolved oxygen and free from carbonic acid so that it may

remain fresh

1.4 Various types of water demands

While designing the water supply scheme for a town or city, it is necessary to

determine the total quantity of a water required for various purposes by the city. As a

matter of fact the first duty of the engineer is to determine the water demand of the town

and then to find suitable water sources from where the demand can be met. But as there

are so many factors involved in demand of water, it is not possible to accurately

determine the actual demand. Certain empirical formulae and thumb rules are employed

in determining the water demand, which is very near to the actual demand.


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different empirical formulae.

For Indian conditions kuichings formula gives satisfactory results.

Q=3182 p

Where Q is quantity of water required in litres/min

P is population of town or city in thousands

1.5 Losses and wastes

All the water, which goes in the distribution, pipes does not reach the consumers.

The following are the reasons

1. Losses due to defective pipe joints, cracked and broken pipes, faulty valves and

fittings

2. Losses due to, consumers keep open their taps of public taps even when they are not

using the water and allow the continuous wastage of water

3. Losses due to unauthorised and illegal connections

While estimating the total quantity of water of a town; allowance of 15% of total

quantity of water is made to compensate for losses, thefts and wastage of water


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sCHAPTER II

LITERATURE REVIEW

2.0 General

2.1 Distribution of water

After treatment, water is to be stored temporarily and supplied to the consumers through

the network of pipelines called distribution system. The distribution system also includes

pumps, reservoirs, pipe fittings, instruments for measurement of pressures, flow leak

detectors etc. The cost of distribution is about 40 to 70% of the total cost of the entire

scheme. The efficiency of the system depends upon proper planning, execution and

maintenance. Ultimate aim is to supply potable water to all the consumers whenever

required in sufficient quantity with required pressure with least lost and without any

leakage.

2.2 Requirement of a distribution system

1. The system should convey the treated water to consumers with the same degree of purity

2. The system should be economical and easy to maintain and operate

3. The diameter of pipes should be designed to meet the fire demand

4. It should safe against any future pollution. As far as possible, it should not be laid below

sewer lines.

5. Water should be supplied without interruption even when repairs are undertaken.


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Advantages

1. In the case of repairs a very small portion of distribution are a will be affected

2. Every point receives supply from two directions and with higher pressure

3. Additional water from the other branches are available for fire fighting

4. There is free circulation of water and hence it is not liable for pollution due to stagnation.

Disadvantages

1. More length of pipes and number of valves are needed and hence there is increased cost

of construction

2. Calculation of sizes of pipes and working out pressures at various points in the

distribution system is laborious , complicated and difficult.

Circular or ring system

Supply to the inner pipes is from the mains around the boundary. It has the same

advantages as the grid-Iron system. Smaller diameter pipes are needed. The advantages

and disadvantages are same as that of grid-Iron system.

..


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Radial system:

This is a zoned system. Water is pumped to the distribution reservoirs and from

the reservoirs it flows by gravity to the tree system of pipes. The pressure calculations are

easy in this system. Layout of roads need to be radial to eliminate loss of head in bends.

This is most economical system also if combined pumping and gravity flow is adopted.

..

2.4 System of distribution

For efficient distribution it is required that the water should reach to every

consumer with required rate of flow. Therefore, some pressure in pipeline is necessary,

which should force the water to reach at every place. Depending upon the methods of

distribution, the distribution system is classified as the follows:

1. Gravity system

2. Pumping system

3. Dual system or combined gravity and pumping system


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..

Combined pumping and gravity system

This is also known as dual system. The pump is connected to the mains as well as

elevated reservoir. In the begining when demand is small the water is stored in the

elevated reservoir, but when demand increases the rate of pumping , the flow in the

distribution system comes from the both the pumping station as well as elevated

reservoir. As in this system water comes from two sources one from reservoir and second

from pumping station, it is called dual system. This system is more reliable and

economical, because it requires uniform rate of pumping but meets low as well as

maximum demand. The water stored in the elevated reservoir meets the requirements of

demand during breakdown of pumps and for fire fighting.


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..

The water may be supplied to the consumers by either of the two systems.

Continuous system

This is the best system and water is supplied for all 24 hours. This system is

possible when there is adequate quantity of water for supply. In this system sample of

water is always available for fire fighting and due to continuous circulation water always

remains fresh. In this system less diameter of pipes are required and rusting of pipes will

be less. Losses will be more if there are leakages in the system.

Intermittent system

If plenty of water is not available, the supply of water is divided into zones and

each zone is supplied with water for fixed hours in a day or on alternate days. As the

water is supplied after intervals, it is called intermittent system. The system has following

disadvantages:

1. Pipelines are likely to rust faster due to alternate wetting and drying. This increases

the maintenance cost.

2. There is also pollution of water by ingress of polluted water through leaks during

non flow periods.


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2.5 Pumps

The function of pump is to left the water or any fluid to higher elevation or at

higher pressure. Pumps are driven by electricity ,diesiel or steam power. They are helpful

in pumping water from the sources, that is from intake to the treatment plant and from

treatment plant to the distribution system or service reservoir . In homes also pumps are

used to pump water to upper floors or to store water in tanks over the buildings.

2.6 Types of pumps and their suitability

Based on the mechanical principle of water lifting, pumps are classified as the

following


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2.7 Selection of pump horse power

Basic data regarding the water availability like diameter, depth of the well, depth

of the water table, seasonal variations of water table, drawdown duration of pumping and

safe yield are to be collected accurately before selecting a pump.

The horse-power (H.P.) of a pump can be determined by calculated the work done by apump in raising the water upto H height.

Let the pump raise w kg of water to height H m Then work done by pump = w X H Kg m

= WQH m kg/sec

Where W density of water in kg/m3.Q water discharge by pump in m3/sec

The water horse power = discharge x total head/( 75)W Q H

W.H.P. = WxQxH/75

Break Horse Power = W.H.P./Efficiency=W. H. P./(75 )


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Where QL Allowable leakage in lit/day

N No. of joints

P Average test pressure

D diameter of pipe in mm

The above value is applicable for C.I, A.C and concrete pipes.

For steel and prestressed concrete pipes 3 times the above value is allowed.

Gravity pipes are tested with hydrostatic head of 2.5m at the highest point in the

pipe for 10minutes permissible leakage is 0.2 litres / mm of diameter pipe per day per

kilometer length.

2.9.4 Maintenance of pipes:

Hygienic quality and adequate flow in the pipe lines are to be maintained,

maintenance of pipes includes the following

1. Detection of leaks in faulty joints ferrule connections, pipes and fittings

inside the consumer premises,

2. Detection of corrosion in pipes, fractures and replacement of these portions

3. The wastage of water 15 to 25% of leakage through pipe joints should be

brought down to the minimum possible extent by adopting suitable

preventive measures

4. Cleaning of pipes by flushing and disinfection of pipes

5. Protection against pollution Water Supply Engineering

6. The records of regarding the lengths of pipe laid, length of pipe repaired or

replaced, expenditure incurred, no. of fire hydrants , no. of service

connections and all other relevant data in connection with the distribution

system should maintained for ready reference.


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2.10.1.1Sluice valve

These are also known as gate-valves or stop valves. These valve control the flow

of water through pipes. These valves are cheaper, offers less resistance to the flow of

water than other valves. The entire distribution system is decided into blocks by

providing these valves at appropriate places. They are provided in straight pipeline at

150-200m intervals. When two pipes lines intersect, valves are fixed in both sides of

intersection. When sluice valve is closed, it shuts off water in a pipeline to enable to

undertake repairs in that particular block. The flow of water can be controlled by raising

or lowering the handle or wheel.

Fig 2.10.1.1 Sluice valve

2.10.1.2 Check valve or Reflex valve

These valves are also known as non-return valves. A reflux valve is an automatic

device which allows water to go in one direction only. The swing type of reflux valve as

shown in fig is widely used in practice.


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water due to air lock. In such cases the accumulated air has to be removed from the pipe

lines. This is done automatically by means of air relief valves.

Fig 2.10.1.3 Air Valve

This valve consists of a chamber in which one or two floats are placed and is

connected to the pipe line. When there is flow under pressure in the pipeline water

occupies the float chamber and makes the float to close the outlet. But where there is

accumulation of air in the pipeline, air enters the chamber, makes the float to come down,

thus opening the outlet. The accumulated air is driven out through the outlet.

2.10.1.4Drain valve or blow off valve

These are also called wash out valves they are provided at all dead ends and

depression of pipelines to drain out the waste water. These are ordinary valves operated

by hand.

2.10.1.5 Scour valve

These are similar to blow off valves. They are ordinary valves operated by hand.

They are located at the depressions and dead ends to remove the accumulated silt and

sand. After the complete removal of silt; the value is to be closed.


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They have long stem with screw and nut to regulate the flow. In case of fire accident ,

the fire fighting squad connect their hose to the hydrant and draw the water and spray

it on fire.

A good fire hydrant

1. Should be cheap

2. Easy to connect with hose

3. Easily detachable and reliable

4. Should draw large quantity of water

2.11 Plumbing system in building

It is necessary to know the following terms relating to plumbing, principles and the

common practices used in the house plumbing

1. Water main: A water supply pipe vests in the administrative authority for the use of

public or community

2. Ferrule: It is gunmetal or bronze screwed into the hole drilled in CI pipe mains.

Communication pipe takes off from the ferrule. The pressure in the domestic supply and

equal distribution among the house connection are effected by adjusting the ferrule

opening. Normally the ferrule opening is equal in area to the area of flow in

communication pipe.

3. Saddle: it is used in place of ferrule for mains of AC or PVC pipes

4. Communication pipes: It is a pipe taking off from the ferrule for the house connection. It

is owned and managed by the water supply authority. Communication pipe terminates at

the boundary of the consumers premises.

5. Service pipe : it is the part of the house connection beyond the stop cock. It is owned and

maintained by the consumer . No pumps shall be installed on this pipe.

6. Watermeter: It is installed to measure the flow. It is an integrating meter that it records


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the total flow upto the time of measurement.

Generally 12.5 mm to 18.75mm rotary water meters are installed either at the beginning

or at the middle of the service pipe. A masonary pit is constructed around it. It has

facility of sealing by the water supply authority

7. Residual pressure: It is generally measured at the ferrule and should be about 7m head of

water

8. Goose Neck: It is the short bent pipe and allow for small changes in length due to

expansion and movement of pipes due to soil settlements. It can also withstand stresses.

2.11.1 Plumbing systems in water supplies

The following are the requirements of plumbing systems in water supplies

1. Plumbing of water lines should be such as not to permit back flow from eistern and

sinks Water Supply Engineering

2. All joints shall be perfectly water tight and no leakage or spill at taps or cocks should be

allowed

3. Pipelines should not be carried under walls or foundations

4. It should not be close to sewers or waste water drains. There should not be any

possibility for cross connections.

5. When pipe lines are close to electric cables proper precautions for insulation should be

observed.

6. plumbing lines should be such as to afford easy inspection and repair of fixtures and

joints.

7. Number of joints should be less and the number of bends and tees should be less

8. It should supply adequate discharge at fixtures economical in terms of material and protected

against corrosion , air lock, negative pressure and noise due to flow in pipes and in flushing


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The house water connections

The house water connection is as shown in the fig

..

2.11.2Stop cocks

It is a valve fitted at the end of communication pipe and it is under the control of water

supply authority. The purpose of stop cock is to stop the supply of water. Temperory

disconnections are made at the stopcock while permanent disconnections are made at

ferrule.

..


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2.11.4 Pipe fittings

In addition to the pipes, valves, tapes, various types of pipe fittings such as

unions, caps, plugs, flanges, nipples, crosses, tees, elbows, bends etc are used during

laying of distribution pipes The common pipe fittings are shown in fig


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2.11.5 Water piping system in building

The following are the requirements of piping system in building

1. Plumbing of water lines should be such as not to permit backflow from cisterns

and sinks.

2. All joints shall be perfectly water tight and no leakage or spill at taps or cocks

should be allowed.

3. Pipelines should not be carried under walls or foundations

4. It should not be close to sewers or waste water drains. There should not be any

possibility for cross connections

5. When pipelines are close to electric cables proper precautions for insulation

should be observed

6. Plumbing lines should be such as to afford easy inspection and repair of fixtures

and joints

7. Number of joints should be less and number of bends and tees should be less

8. It should supply adequate discharge at fixtures, economical in terms of materials

and protected against corrosion, airlock, negative pressure and noise due to flow

in pipes and in flushing.

2.11.6 Piping system using direct supply

When the residual pressure at the ferrule is greater than 7m and continuous supply

is available in the mains, water may be supplied directly from the service pipe for various

fixtures for a single storey building.

2.11.7 Piping system using over head tanks

If the supply is intermittent and residual pressure is low then, water is pumped to

over-head tanks and then supplied to distribution pipes at required pressure by gravity


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Fig 2.11.5 piping system using overhead tanks

If the supply is intermittent and residual pressure is low then a ground level

storage tank and a overhead storage tank are built to supply water. Water from the

overhead tank is drawn by down take pipes and then into the distribution pipes for

fixtures.

2.11.8Pumped systems

When the residual pressure at the ferrule is less than 7m and continuous supply is

available in the mains, water may be supplied by pumping from the service pipes.


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2.12 Intensity of pressure

When a liquid is contained in a vessel, it exerts force at all points on the sides and bottom

of the container. This force per unit area is called intensity of pressure. If p is the total

force acting on the cross sectional area a Y

then intensity of pressure p = P/a.

The direction of this pressure is always at right angles to the surface, with which the fluid

at rest, comes in contact.

2.12.1 Pressure head

The vertical height of the free surface above any point in a liquid at rest is known as

pressure H = p / w

P = wh

This equation shows that the intensity of pressure at any point in a liquid is proportional

to its depth from the liquid surface.

The pressure may be expressed as

1. Force per unit area in N/m2

2. Height of the equivalent liquid column in cm or m

Units The pressure is expressed in pascal (pa)

Loss of head due to friction

When the water is flowing in a pipe, it experiences some resistance to its motion. This

reduces the velocity and ultimately the head of water available. The major loss is due to

frictional resistance of the pipe only.

Darcys formula is used to calculate the loss of head in pipes due to friction; neglecting

minor losses

Hf = 4 f l v2/ 2g d

where f frictional resistance


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lLength of pipe

ffrictional resistance

vvelocity of water in the pipe

ddiameter of pipe

hfloss of head due to friction

QLdischarge through pipe

2.12.2 Loss of head due to sudden enlargement

Fig 2.12.2


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2.12.3 Loss of head due to sudden contraction

Fig 2.12.3


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Loss of head due to bends

When the direction of a length changes such as at the bends in a pipe line, some of the

liquid energy is lost.

Loss of head due to bends = k V2/2g

Where

k coefficient which depends upon angle and radius of bend

K = 1 for 90 elbows

V = Velocity of liquid in the pipe

g = acceleration due to gravity

Loss of head at the entrance

The loss of head due to entrance in a pipe is actually a loss of head due to sudden

contraction and depends upon the form of entrance.

Loss of head at entrance = 0.5V2/ 2g

where



Loss of head due to exit

The loss of head due to exit in a pipe is actually a loss due to energy of head of flowing

liquid by virtue of its motion.

Loss of head at exit by experimentally = V2/ 2g

where




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CHAPTER 3

STUDY AREA

The study area where the project work done is BLOCK-IV OF GOKARAJU RANGARAJU

INSTITUTE OF ENGINEERING AND TECHNOLOGY(G.R.I.E.T) BACHUPALLY,

HYDERABAD.

G.R.I.E.T is located in bachupally, 5km from jntu having an area of 65 acres.

The engineering college comprises of four blocks besides a block for pharmacy, sheds for

mechanical workshops and a vast playground.

Our project is done on block-IV which is allocated for civil engineering, mechanical engineering

and bio-technology engineering disciplines.

Block-IV comprises of five storeys. Height of each storey is 13.5 ft. the total height of building is

67.5 ft.

The population of the building is 946

The project work includes design of water supply and sanitation system for the block- IV.

Design of water supply includes

Calculation of pressure heads at bends, head losses in pipes, calculation of pipe diameters.

Design of sanitation system includes the design of septic tank.


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The general relationship between head loss and flow is:

where r is the head loss per unit flow and n is the flow exponent. In most design situations

the values that make up r, such as pipe length, diameter, and roughness, are taken to be

known or assumed and the value of r can be determined for each pipe in the network. The

values that make up r and the value of n change depending on the relation used to determine

head loss. However, all relations are compatible with the Hardy Cross method.

It is also worth noting that the Hardy Cross method can be used to solve simple circuits and other

flow like situations. In the case of simple circuits,

is equivalent to

.

By setting the coefficient r to R, the flow rate Q to I and the exponent n to 1, the Hardy

Cross method can be used to solve a simple circuit. However, because the relation

between the voltage drop and current is linear, the Hardy Cross method is not necessary

and the circuit can be solved using non-iterative methods


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The method of balancing heads uses an initial guess that satisfies continuity of flow at each

junction and then balances the flows until continuity of potential is also achieved over each loop

in the system.

Proof

If the initial guess of flow rates in each pipe is correct, the change in head over a loop in the

system, would be equal to zero. However, if the initial guess is not correct, then the

change in head will be non-zero and a change in flow, must be applied. The new flow

rate, is the sum of the old flow rate and some change in flow rate such that

the changed in head over the loop is zero. The sum of the change in head over the new loop will

then be .

The value of can be approximated using the Taylor expansion.

For a small compared to the additional terms vanish, leaving:

And solving for


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The change in flow that will balance the head over the loop is approximated

by . However, this is only an approximation due to the

terms that were ignored from the Taylor expansion. The change in head over the

loop may not be zero, but it will be smaller than the initial guess. Multiple

iterations of finding a new will approximate to the correct solution

Process

The method is as follows:

1. Guess the flows in each pipe, making sure that the total in flowis equal to the total outflowat each junction. (The guess doesn't have to be good, but a good guess will reduce

the time it takes to find the solution.)

2. Determine each closed loop in the system3. For each loop, determine the clockwise head losses and counter-clockwise head losses.

Head loss in each pipe are calculated using . Clockwise head losses are from

flows in the clockwise direction and likewise for counter-clockwise.

4. Determine the total head loss in the loop, , by subtracting the counter-clockwisehead loss from the clockwise head loss.

5. For each loop, find without reference to direction (all values should bepositive).

6. The change in flow is equal to .


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7. If the change in flow is positive, apply it to all pipes of the loop in the counter-clockwisedirection. If the change in flow is negative, apply it to all pipes of the loop in the

clockwise direction.

8. Continue from step 3 until the change in flow is within a satisfactory range.

Method of balancing flows

The method of balancing flows uses an initial guess that satisfies continuity of potential over

each loop and then balances the flows until continuity of flow is also achieved at each junction.

Advantages of the Hardy Cross method

Simple math

The Hardy Cross method is useful because it relies on only simple math, circumventing the need

to solve a system of equations. Without the Hardy Cross methods, engineers would have to solve

complex systems of equations with variable exponents that cannot easily be solved by hand.

Self correcting

The Hardy Cross method iteratively corrects for the mistakes in the initial guess used to solve the

problem. Subsequent mistakes in calculation are also iteratively corrected. If the method is

followed correctly, the proper flow in each pipe can still be found if small mathematical errors

are consistently made in the process. As long as the last few iterations are done with attention to


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detail, the solution will still be correct. In fact, it is possible to intentionally leave off decimals in

the early iterations of the method to run the calculations faster.


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Where

K = L

470 d4.87

Computation of K values for pipes of network of fig. 5.2

Table 1

Pipe Length in meter Dia in meter K = L / 470 d4.87

For loop ABCDA

AB 500 0.30 374.4

BC 300 0.20 1618

CD 500 0.20 2696.8

DA 300 0.20 1618

For loop DCFED

DC 500 0.20 2696.8

CF 300 0.15 6568.4

FE 500 0.15 10947

ED 300 0.15 6568.4

Now both the loops are analysed for Hardy Cross method procedure in table 2


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Table2: Table for loop ABCDA

Pipe assumed Flow K value HL= HL/ Qa= corrected flowafter

l/s m3/s from tb1 KxQa

1.85col5/ col3 1

stcorrection Qa1=

Col 2+ l (l/s)

1 2 3 4 5 6 7

AB 45 .045 374.4 (+)1.21 26.89 47

BC 23 .023 1618 (+)1.51 65.65 25

CD (-) 15 (-).015 2696.8 (-)1.14 76.0 (-) 13.0

DA (-)30 (-).030 1618 (-)2.46 82.0 (-) 28.0

HL=-.88 250.54

then l= (-)H

L (-)0.88 1.899m3/sec

x.HL 1.85 x 250.54

Qa

Or 1=(+)1.90 l/s

(say) (+)2 l/s


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Table for loop DCFED

1 2 3 4 5 6 7

DC 15 0.015 2696.8 (+) 1.14 76 10

CF 23 0.023 6568.4 (+) 6.12 266 18

FE (-) 8 (-)0.008 10947 (-) 1.45 181.3 (-) 13

ED (-) 5 (-)0.005 6568.4 (-)0.36 72 (-) 10

HL=(+)5.45 595.3

Then the 1stcorrection for loop DCFED

1= (-)HL (+) 5.45 (-) 4.95 x 10

-3 m3/sec

x. HL 1.85 x 595.3

Qa

Or 1= (-) 4.95 l/s.

(say) (-)5 l/s.


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Then the corrected discharge after first corrections in various pipes are now given as

Pipe Corrected discharges after first corrections in l/sec.

For loop ABCDA

AB (+) 47

BC (+) 25

CD (-) 13

DA (-) 28

For loop DCFED

DC (+) 10

CF (+) 18

FE (-) 13

ED (-) 10

Discharge in pipe common to both loops i.e. pipe CD

= assumed discharge + 1+ 1= -15 + 2 (-)5

= -15 + 2 + 5 = (-) 8 l/sec.

Since correction of (-) 5 l/s is in pipe DC and hence it will be equal to (+) 5l/s in pipe CDThese discharges are now again used to re-analyse both the loops for the second correction in

table 3.


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Roughness of steel pipe k= 0.1mm

1stcase. Cast iron pipe

We should first find the value of friction factor using

(1/f ) = 2 log10(RO/k) + 1.74 . (1)

= 2 log10(100/0.3) + 1.74

= 6.78

therefore f = (1/6.78)2= 0.02

local losses are to be neglected. This means head loss due to friction is to be considered. Head

loss due tot friction is

4 = (f x L x V

2

) / (d x 2g)

= (0.02 x 500 x V2) / (0.2 x 2 x 9.81)

V = 1.25 m/s.

Discharge Q1= V x area = 1.25 x (/4) x d2

= 1.25 x 0.78 x 0.22

= 0.0392 m3/s

2nd

case. G.I. pipe

K = 0.1mm, Ro= 500mm

Substituting these values in equation (1), we get

(1/f) = 2 x log10(100/0.1) + 1.74 = 7.74

f = (1/7.74)2= 0.0166

head loss due to friction, 4 = (f x L x V2) / (d x 2g)

= (0.0166 x 500 x V2) / (0.2 x 2 x 9.81)

V = 1.375 m/s

Therefore discharge, Q2= V x Area = 1.375 x (/4) x 0.22


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= 0.0431 m3/s

Percentage increase in the discharge = ((Q2 Q1) / Q1) x 100

= ((0.0431 0.0392) / 0.0392) x 100

= 9.94 %

Calculation of head loss

Diameter of pipe is 200mm

Assuming water flows with avelocity of 3m\s

For a length of 5m

Kinematic viscosity of water as v = 0.01 stoke = 0.01 x 10-4

m2/s.

the head lost due to friction is computed as follows:

Darcy Formula is given by

hf = (4 x f x L x V2) / (d x 2 x g)

Where f = coefficient of friction is a function of Reynolds number, R e

But Reis given by Re = (V x d ) / v.

= (3.0 x 0.20) / (0.01 x 10-4

)

= 6x 105

Therefore value of f = (0.079 / (Re)1/4

)

= (0.079/ (6 x 105)

1/4)

= 0.00283

Therefore head lost hf = (4 x 0.00283 x 5 x 32) / (0.2 x 2 x 9.81)

= 0.1298 m


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5.3 Design of septic tank

Design of septic tank for 946 users, assuming the rate of water supply as 66 litres/head/day.

Solution:

Assuming the detention period as 24 hours and the time of cleaning the sludge as 3 years.

Space required for settling = (946 x 66) 1000 = 62.4 m3

Space required for digestion = (946 x 0.0425) = 40.2 m3

Space required for storage of sludge = (946 x 0.085) = 80.41 m3

Total space required = (62.4 + 40.2 + 80.41) = 183.01 m3

Providing depth as 1.2 m,

Surface area = 25 m2

Now assuming L: B=1:1

Then (B x B) = 25 m2

Or B = 5 m, L =5 m.

Providing free board as 30 cm

Then overall depth =1.2 + 0.3 =1.5 m

Therefore provide the septic tank of size = 5 m x 5 m x 1.5 m.


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Fig 5.3.1 Septic tank


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Fig 5.3.2 pipe line layout


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CHAPTER 7

CONCLUSION

For an effective water supply system,Initially, water demand is calculated based on the purpose of the building and the

population of the building. Allowances are given as per the given codal provisions.

For an effective water distribution system,Layout is prepared

Diameters of pipes are calculated

Pressures in pipe lines are calculated

Loss in pressure head is calculated

Discharge is compared for cast iron pipe and G.I. pipe

Discharge in pipe network is calculated using hardy cross method

Also, the discharge can be verified using softwares such as EPANET, LMNO, WESNET For sanitation purpose, Septic tank is designed.


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CHAPTER 8

REFERENCES

IS 2065-1963 IS 1172-1963 NATIONAL BUILDING CODE (N.B.C.) A TEXTBOOK OF ENVIRONMENTAL ENGINEERING BY G.S.BIRDIE and

J.S.BIRDIE

A TEXTBOOK OF FLUID MECHANICS AND HYDRAULIC MACHINERY BYMODI &SETH

SOFTWARES SUCH AS EPANET LMNO WESNET WIKIPEDIA


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water supply to griet

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